On any car if you get a check engine light or other fault light this typically means one or more of the sensors has failed or has a faulty connection.The fault can be something quite simple and nothing that’s going to stop the car to something quite major that will reduce engine power and possibly stop the engineThe ECU senses this and may put the car into 'limp home' mode which typically limits the revs and the amount of power available. Usually the car is safe to drive for a short distance as the mode is intended is intended to get you home without incurring any engine damageThe quickest route to repair is to have the car plugged into a diagnostic machine which will read off the fault code stored in the ECU (providing the light is still on at this point) and indicate which sensor has failed or whether the fault is more serious.However from your description this could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak. Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident. Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engineMight also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.if the engine condition is the same then chances are the meter or the connection to it is faultyAir leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.This leads them to be quite intermittent in the case of mild leaksits also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residueOn no account touch the sensor wires with anything physical as they are extremely fragile
Thanks for your response Matt, wifey drove the car to work this morning (40 minutes mostly motorway) and said the warning light was illuminated all the way.
You list many possible causes, starting from the top - I'll take it to a garage to get it checked for air leaks tomorrow (assuming wifey gets it home tonight)!
Thanks for your response, you suggested many possible faults, I'll start at the top of your suggestions, work my way down and hopefully you and my garage will cure the problem soon. I'll rate your answer when either you cure the problem or I dispose of the car. I assumed we'd chat during the diagnostic process.
Sorry for the delay, I took the car to the garage and they said the problem was the Coil which they replaced under the manufacturer's warranty.
No thanks, ***** ***** do I need to do now on this site?